We advocate for an honest and transparent conversation about the CO2 emissions associated with our products.

We advocate for an honest and transparent conversation about the CO2 emissions associated with our products.

As the world increasingly acknowledges the reality of climate change and the crucial role of sustainable practices, understanding the carbon footprint of materials, such as aluminium, becomes vital. However, when it comes to aluminium recycling, not all processes are created equal - a fact that can result in confusion and misinterpretation. 

Aluminium is prized for its durability, lightness, and infinite recyclability, making it an ideal material for a circular economy. This has led to the offering of recycled aluminium as a greener alternative by many manufacturers. Nevertheless, the environmental impact of this recycling is contingent on the origin of the material and whether it has been used in a product before. 

If the recycled aluminium is from used windows, doors, façades (post-consumer scrap), its CO2 footprint is close to zero, as recycling aluminium only requires 5% of the energy it takes to produce it the first time around. Post-consumed scrap is therefore the greenest recycled aluminium. 

Aluminium can also be recycled from production waste, or pre-consumer scrap. As this aluminium has never been used in a product and had a useful life before, it carries with it the same CO2 footprint as the original aluminium – plus 5% from the recycling process. 

Ask what’s inside your recycled aluminium

Some aluminium producers merge pre- and post-consumer scrap in their calculations, which could incentivize waste production and misrepresent high carbon footprint aluminium as zero carbon scrap. The key, then, is transparency: understanding the methods of calculation and documentation of the product you are purchasing. This allows you to get an accurate picture of the actual environmental impact of your recycled aluminium. 

As a customer of recycled aluminium,you should always ask:​  

  • What is the CO2 footprint of my product? ​ 
  • How do you calculate the CO2 footprint? 
  • How do you document the product you sell? 


When it comes to pre-consumer scrap, however, there is an ongoing debate regarding its classification in life cycle assessment (LCA) studies. Unlike post-consumer scrap, pre-consumer scrap has never lived as a product (never consumed) and its associated CO2 emissions are fresh. Furthermore, pre-consumer scrap holds positive financial value, often being sold to external recyclers. 

In addition, if your product comes with an Environmental Product Declaration (EPD) the document should describe the shares ofpre-and post-consumer scrap, alongside the global warming potential (the “CO2 footprint”) and the additional environmental impacts of the product. 

Two methods of calculating the carbon footprint of aluminium scrap

The confusion lies in the absence of clear guidance from international standards on the best method of carbon footprint calculation for pre-consumer scrap. There are two commonly used methods: the cut-off approach and the avoided burden approach. While both methods are valid, they deliver drastically different results. 

  • The cut-off approach: Here, the footprint follows the main product because there is no environmental burden for the scrap. 
  • The avoided burden approach: In this case, the footprint follows the material, with the burden shared between every output (ingot and scrap). 


The main reason the two scrap types are considered equivalent is because the avoided burden approach implies the ability to fully trace the scrap. The cut-off approach, due to its simplicity, is often preferred, but it could hinder the development of the circular economy by not giving post-consumer scrap a carbon footprint advantage. This could potentially encourage the use of pre-consumer scrap, overshadowing the sustainability goal of reducing and avoiding scrap in the production process. 

In light of the debate, the priority should be transparency, offering data for either calculation method. In a world that increasingly values sustainability, vague claims of being "sustainable" or "recycled" are no longer sufficient. It's imperative that we accurately define these terms, share data openly, and encourage verification. 

The philosophy at Hydro Building Systems aligns with this vision. We believe that the avoided burden approach is a good way to get a realistic picture of the carbon emissions and incentivize a circular economy. We advocate for an honest and clear conversation about the CO2 emissions associated with our products. We firmly believe that through understanding, innovation, and commitment to sustainability, we can lead the way in demonstrating that recycled aluminium is not just a buzzword, but a viable, responsible choice for the future. 


See how we can help your project meet sustainability standards.

Contact us